The activity of cytosolic phospholipase A2 (cPLA2) may be altered by calcium or by phosphorylation of serines in the cPLA2 molecule. A dual hybridization system in yeast was used to identify protein-protein interactions which might also be involved in the modulation of cPLA2 activity. Using this system, a member of the S-100 family of proteins (p11) was identified as interacting with cPLA2. The promoter region of the p11 gene has been cloned and characterized. Recombinant cPLA2 has been produced in bacteria and in insect epithelial cells. Treatment of these proteins with thiol modifiers reduces activity. Treatment with S-nitroso-glutathione also alters activity. Ongoing studies include production of recombinant protein and modulation of enzyme function by oxidant molecules.